Replaced O2 sensor, now have check engine light on. Any help out there JLevie???

[txtorquemade]

Now my 87 325is ,,, is causing problems.

History:

Has been pulling poorly, would ont redline, or even r3v.
Last week, starting making a ticking, valvetrain sounding noise under load, but no redline, hardly over 3-3.5 k top RPM.

Then started a horrible "rattle" sound. NOT anything I can identify. Maybe manual tranny, maybe cat.. maybe ....well, I dunno. Those are my best two guesses.

Throws a o2 sensor light, check engine light. Starts the rattle, even louder, missing, and very erratic idle.

Ok I replace the O2 sensor. Man that biotch is hard to get our, then back in. I couldnt get it screwed all the way in so took it to a cheap Indy shop up the street to just screw it down.

Picked up the car, no check engine light. Seemed to start and idle alright. On the way home there is no "rattle". I get into my driveway, just about to operating temp and the rattle starts, but is back to be very intermittent and subdued. Throws check engine light. Still idles fine.

I decide to drive it today to check it out. Start up. No check engine light. Idle is puuuurfect. Just a hint of the prior "rattle' noise. I get out and try to redline....Still not pulling to redline. Sluggish, and slow. But idles fine.

Check engine light come on about the time I hit operating temp. No smells or other problems. The "rattle" is absent for the most part.

I decide to just hold the accelerator down... and pushing the car, rowing the gears, downshifting and keeping up as high in the rev band as possible. I feel a pop, not really hear but it was like something blew through the fuel line, cat, something.... opened up... and the car started redlining and pulling harder and smoother than it has since Ive had it. I assume the new O2 sensor is the reason, but... still has check engine light on (O2 sensor light is off still). The car pulls like it never has, sounds good, no excessive valvetrain noise.

What could be causing my check engine light? What is the rattle? Im thinking the cat is maybe restricted, plugging. I know I need to pull the codes but I dont have a Peak. The lil Indy shop didnt have one for BMW, or OBD I, which I think a 12/86 build date, 1987 model 325is is, right?

Any ideas? Before I spend 100 bucks on getting codes pulled at a decent Indy shop?

[jlevie]

You definitely need to pull the codes to see what they point to. Nothing in the symptoms points to an obvious fault, but I'm going to guess that the noise is either misfires or an exhaust leak.

[txtorquemade]

Why does exhaust leak sound likely? Maybe the shop didnt get the lamba screwed in deep enough?

CAN it leak when the damn thing is so tight I had to use a breaker bar to insert it?

Can I "stomp test" this?

Thanks JLevie, you always seem to lead to the correct solution. You da man!

[jlevie]

Depending on were an exhaust leak is and how bad it is, it can sound like a tick, rattle, etc. I doubt that it would be from the O2 sensor, but you could have a leak elsewhere in the exhaust.

Misfires can be caused by a number of things, but intake leaks head the list. Intake leaks can also result in a Lambda fault, which in turn can be caused by a bad O2 sensor. The life of the O2 sensor is not more than 100k, so its replacement was probably warranted, even if it failed to resolve the CEL. A smoke test of the intake would be the next step.

[txtorquemade]

I should mention. The car is pulling stronger than it ever has. No exhaust smell. Only problem now is the CEL. No obvious vacuum leaks.

Im kinda stumped without pulling codes.

[jlevie]

You are going to have to take the car to a shop that can read the fault code(s).

[AndrewBird]

I would almost bet your cat is/was plugged. I went through almost the exact same thing on my Jetta. Car is sluggish, won't rev and a weird rattling noise. Turned out the honeycomb mesh inside the cat had broken loose and was rattling around inside the cat. I ended up just cutting the cat out and straight piping it.

[txtorquemade]

I would almost bet your cat is/was plugged. I went through almost the exact same thing on my Jetta. Car is sluggish, won't rev and a weird rattling noise. Turned out the honeycomb mesh inside the cat had broken loose and was rattling around inside the cat. I ended up just cutting the cat out and straight piping it.

Ok.. its not making the rattling noise now and it WILL rev and pull to redline. But, the ticking/pinging noise is back. When the new O2 sensor went it, it was still pulling crappy UNTIL I was flooring it for a good while and it seemed something, unplugged and thats when it started pulling and redlining great. Idle was smooth. Big difference. No rattle, no ping/tick.

Now... it ticking/pinging again and idling a little bit off. Not like it was though. Still pulling hard.

Im kinda stumped. I started a new thread on this topic earlier today, so anyone thinking Im ADD or something.. eh, no. Just really at a loss.

I will use my brand new Peake Tool, with adapter on it later today though.